A precision analysis and determination of the technical requirements of an atom interferometer for gravity measurement

The influence of the wave-front curvature of Raman pulses on the measurement precision of gravitational acceleration in atom interferometry is analysed by the method of a transmission matrix. It is shown that the measurement precision of gravitational acceleration is largely dependent on the spot size of the Raman pulse, the temporal interval between Raman pulses and the optical path difference of the two counter-propagating Raman pulses. Moreover, the influence of Doppler frequency shift on the precision is discussed. In order to get a certain measurement precision, the requirement for the accuracy of frequency scanning of the Raman pulse to compensate for the Doppler frequency shift is obtained.      

Experimental progress in gravity measurement with an atom interferometer

Precisely determining gravity acceleration g plays an important role on both geophysics and metrology. For gravity measurements and high-precision gravitation experiments, a cold atom gravimeter with the aimed resolution of 10.⁻⁹g/Hz^1/2 (1 g=9.8 m/s²) is being built in our cave laboratory. There will be four steps for our ⁸⁷Rb atom gravimeter, Magneto-Optical Trap (MOT) for cooling and trapping atoms, initial state preparation, π/2-π-π/2 Raman laser pulse interactions with cold atoms, and the final state detection for phase measurement. About 108 atoms have been trapped by our MOT and further cooled by moving molasses, and an atomic fountain has also been observed.      

基于冷原子重力仪的绝对重力动态移动测量实验

动态重力测量可以提高重力场的勘测效率,对基础地质调查、资源勘探、地球物理研究等具有十分重要意义.本文基于冷原子重力仪、惯性稳定平台和牵引动力装置搭建了一套绝对重力动态移动测量系统,并开展了绝对重力动态测量实验.首先测量了不同牵引速度下的垂向振动噪声功率谱,理论分析了其对动态重力测量的影响;其次评估了不同牵引速度对原子干...     

Vibration compensation of an atom gravimeter

For most atom interferometers, the vibration isolation unit is applied to reduce vibration noise. In our experiment, instead of isolation, the vibration signals are monitored, and combining with the sensitive function, the compensation phase shift for the atom interferometer is obtained. We focus on the correction over a wide spectrum rather than on "monochromatic" frequencies. The sensitivity of the atom gravimeter can be upgraded by a factor of more than two. Furthermore, we demonstrate that the atom interferometer can still produce a good measurement result without passive vibration isolation in extremely noisy environments by using vibration compensation.     

First gravity measurements using the mobile atom interferometer GAIN

We present the compact Gravimetric Atom Interferometer (GAIN), based on laser-cooled ⁸⁷Rb atoms, and discuss its first measurements of the local gravitational acceleration. In this context, we also describe an active vibration isolation system and a tip-tilt stage, which allow for a suppression of vibrational noise and systematic effects like the Coriolis force due to Earth’s rotation.     

Participation in the absolute gravity comparison with a compact cold atom gravimeter

The first Asia-Pacific Comparison of Absolute Gravimeters(APMP.M.G-K1) was organized by the National Institute of Metrology(NIM) of China from December 21, 2015 to March 25, 2016 in Changping, Beijing. Our compact cold atom gravimeter(CCAG) was transported from Hangzhou to Beijing with a long distance of about1200 km to participate in this comparison. The CCAG is the only one, to the best of our knowledge, that is based on the principle of atom interferometry among all the instruments. Absolute gravity in the indicated three test sites has been measured as requested by the organizer. The sensitivity of our CCAG is estimated to be90 μGal∕Hz p, even when the measurements are carried out without any vibration isolation. Besides, the accuracy of this gravimeter has been evaluated to be about 19 μGal by considering the significant system errors.Our results show a good agreement with the given reference value.     

Development of an atom-interferometer gravity gradiometer for gravity measurement from space

Recent progress in cold atom interferometry has lead to a new method of sensitive inertial sensing. Significant performance enhancement of cold atom interferometer-based sensors is anticipated when operated in the microgravity environment in space. Based on cold atom interferometer techniques, we are developing a quantum gravity gradiometer for satellite-based global gravity field mapping. As a first step, we have built a laboratory-based gradiometer employing component technologies suitable for a future flight instrument. This paper describes the implementation of the laboratory instrument and its initial results. PACS 03.75.Dg; 39.20.+q; 32.80.Pj; 04.80.-y     

用于位移精密测量的光外差马赫-泽德干涉仪

本文介绍了我们研制的用于位移精密测量的光外差马赫－泽德干涉仪。由于在光路设计中采用了共光路的布置，共模抑制技术得以实现，环境干扰产生的噪声得到很好的消除，相位检测的稳定性和精度大大提高。使用该干涉仪测量了一台在光学相移器内ＰＺＴ微位移驱动装置的电压－位移关系。测量结果具有良好的线性和重复性，与预期相符。根据测量数据分析，该光外差干涉仪具有３ｎｍ的位移测量精度。     

A new lateral shearing interferometer for precision surface measurement

A new lateral shearing interferometer is proposed for precision surface measurement. In this shearing interferometer, a novel shear generator made of a single birefringence crystal plate is utilized. The shear adjustment is realized through the change of angle at which tested wavefront is incident into the crystal plate. By changing the orientation of the principal section of the plate, the generator can adjust the shearing direction. With the incident beam being circularly polarized, the generator can equalize the intensities of two shearing beams to make a good contrast interference pattern. The interferometer is simple and compact in terms of mechanism and has a complete common optical path structure. Phase shifting can be realized conveniently. The interferometer is insensitive to external vibrations and environmental disturbances, and hence has good stability and reliability with high measurement accuracy. To examine the performance of the proposed interferometer, experimental testing was conducted. High accuracy and repeatability are demonstrated.     

光脉冲序列对三能级原子重力仪测量精度的影响

提出了一种通过改变激光脉冲序列来提高三能级原子重力仪测量精度的方法.利用提出的描 写原子运动的3×3阶矩阵方法，分析了三能级原子与双色光场的正交相互作用，计算了 原子干涉仪中的相位差，得到了原子重力仪的相位差与重力加速度的关系.发现通过选择合 适的光脉冲序列，可以提高三能级原子重力仪的精度. 关键词： 原子光学 原子重力仪 矩阵方法     

大倾斜角度下基于冷原子重力仪的绝对重力测量

冷原子重力仪的倾斜角会对绝对重力测量产生显著的影响.高精度的绝对重力测量需要对重力仪的倾斜角进行精确的测量、控制及校正.本文从理论上分析了四种不同情况下倾斜对绝对重力测量的影响规律,并在实验上对得到的理论进行了实验验证.基于此,设计了一种基于双倾斜计的绝对重力测量方案,主要是为了解决恶劣测量环境下的冷原子重力仪倾斜漂移问题.此方案利用高精度倾斜计记录放置在被动隔振平台上的拉曼反射镜的倾斜角度,并使用另外一个倾斜计监控真空系统的倾斜,以实现振动噪声的抑制和倾斜的高精度测量.基于自研的小型化冷原子重力仪,对该方案进行了实验验证,并最终实现了车间复杂环境下的高精度绝对重力测量.由于倾斜得到精确测量和补偿,冷原子重力仪的测量精度达到了12.3μGal.本文为复杂环境下的高精度绝对重力测量提供了一种可行的方案,为冷原子重力仪的实用化提供了参考数据.     

基于原子重力仪的车载静态绝对重力测量

目前大多数原子重力仪的装置复杂、体积庞大、环境适应性差,不能应用于野外进行绝对重力测量,这限制了原子重力仪的应用领域.本文利用自研的小型化原子重力仪,集成了一套车载绝对重力测量系统.该系统主要由原子重力仪、被动平台隔震系统、位姿平台调平系统、差分GPS测高系统、不间断电源供电系统及车载空调温控系统等组成.首先,本文对该测量系统的车载环境适应性进行了评估,发现在野外40℃高温、8°大倾角普通路面的环境下,该系统仍然能够正常工作;其次,介绍了车载绝对重力测量的实验步骤及数据处理方法,并测量了车头朝向对绝对重力测量的影响.最后,在野外平坦路面上进行了重复测线工作,评估了系统的内符合绝对重力测量精度,结果约为30μGal;在野外大倾角山体路面,通过测量不同海拔高度点的绝对重力值,得到了地球的垂直重力梯度值,约为-231(36)μGal/m.本文结果为野外绝对重力勘测提供了依据.     

An atom interferometer for measuring loss of coherence from an atom mirror

We describe an atom interferometer to study the coherence of atoms reflected from an evanescent wave mirror. The interferometer is sensitive to the loss of phase coherence induced by the defects in the mirror. The results are consistent with and complementary to recent measurements of specular reflection.Received: 3 August 2004, Published online: 26 October 2004PACS: 03.75.Be Atom and neutron optics - 03.75.Dg Atom and neutron interferometry - 39.20. + q Atom interferometry techniques The Laboratoire Charles Fabry is part of the Federation LUMAT, FR2764 du CNRS.     

Precision measurement of gravity with cold atoms in an optical lattice and comparison with a classical gravimeter

We report on a precision measurement of gravitational acceleration using ultracold strontium atoms confined in an amplitude-modulated vertical optical lattice. An uncertainty Δg/g ≈ 10(-7) is reached by measuring at the 5th harmonic of the Bloch frequency. The value obtained with this microscopic quantum system is consistent with the one measured with a classical gravimeter. Using lattice modulation to prepare the atomic sample, we also achieve high visibility of Bloch oscillations for ～ 20 s. These results can be of relevance for testing gravitational redshift and Newtonian law at micrometer scale.     

Space tests of relativistic gravity with precision clocks and atom interferometers

Precision clocks and interferometers in space can test relativistic gravity with extremely high sensitivity. Yet, only a single such test has been performed, namely the celebrated flight of a hydrogen maser in a sub-orbital trajectory in 1976 (GP-A mission). This paper suggests some of the obstacles to space flight of precision instruments, and describes how the emergence of new technology might offer a pathway for removing those obstacles. A brief review of emerging technologies is made, and new mission concepts based on them are described. Some of the technologies that can impact more tests of relativistic gravity in space at a more distant future are also described.     

利用原子干涉仪的相位调制进行绝对转动测量

提出一种基于原子干涉仪的相位调制进行绝对转动测量的方法.以π/2-π-π/2构型的空间型原子干涉仪为例，通过对拉曼激光进行相位调制，然后在动量谱空间测量转动对原子速度谱的调制周期，获得原子干涉仪相对惯性空间的绝对转动.文章对于采用该法进行角速度测量的测量范围以及对相位调制频率的要求进行了分析，对于散粒噪声限下的转动测量灵敏度及其影响因素进行了仿真.     

Measurement of the gravitational acceleration of an atom with a light-pulse atom interferometer

Velocity sensitive stimulated Raman transitions have been used to measure the gravitational acceleration, g, of laser cooled sodium atoms in an atomic fountain geometry. By using an improved scheme to drive the Raman transitions, we have demonstrated a resolution of 3×10^–8 g after 2×10³ seconds of integration time. In addition to presenting recent experimental results, we review the theory of stimulated Raman transitions as it applies to atom interferometers and discuss the prospects of an atom interferometer-based gravimeter with better than 10^–10 g absolute accuracy.     

利用原子干涉仪的相位调制进行绝对转动测量

提出一种基于原子干涉仪的相位调制进行绝对转动测量的方法.以π/2-π-π/2构型的空间型原子干涉仪为例,通过对拉曼激光进行相位调制,然后在动量谱空间测量转动对原子速度谱的调制周期,获得原子干涉仪相对惯性空间的绝对转动.文章对于采用该法进行角速度测量的测量范围以及对相位调制频率的要求进行了分析,对于散粒噪声限下的转动测量灵敏度及其影响因素进行了仿真. 关键词： 原子干涉仪 原子陀螺 相位调制 绝对转动测量     

船载系泊状态下基于原子重力仪的绝对重力测量

重力场是反映地球质量分布及变化的重要参数,动态重力测量在地质调查、地球物理、资源勘探等领域有着重要应用.目前动态重力测量均基于相对测量原理,动态相对重力仪存在零点漂移问题,影响其测量性能.动态绝对重力仪可以为相对重力仪提供同步同址校准,解决其长漂问题,因此备受关注.本文基于原子重力仪和惯性稳定平台,搭建了一套船载绝对重力动态测量系统,并在船载系泊状态下开展了绝对重力动态测量实验.经评估,船载系泊环境下的重力测量灵敏度为16.6 mGal/Hz^-1/2,1000 s积分时间内重力测量的分辨率可达0.7 mGal.通过两周的绝对重力测量,评估了系统的稳定性.为了评估绝对重力的动态测量精度,将船上测量点与码头高精度绝对重力基准点的绝对重力值进行了比较,两点之间的绝对重力值差及其不确定度评估结果为(–0.072±0.134)mGal.本文结果为海洋相对重力仪的同时同船校准提供了一种新方案.     

高精度干涉仪针孔空间滤波器研制

应用于高重复频率、高功率193 nm准分子激光器会聚光路中的针孔空间滤波器,除了需要考虑它的材料加工难易、厚度、针孔尺寸等因素外,还需考虑材料抗激光损伤特性。本文利用激光损伤理论中一维热流模型对无限厚和有限厚不同金属样品在高峰值功率193 nm 准分子激光器照射下的损伤阈值进行了分析。结果表明：铝材料在厚度为1.2μm处比其它金属的损伤阈值高,可达1.16×1010 W/cm2,且材料易于加工。利用聚焦离子束技术加工了航空铝材料样品,得到了厚度为1.2和1.5μm的针孔空间滤波器样品。扫描电镜观察其具有较好圆度和内壁粗糙度,基本满足剪切干涉仪对针孔空间滤波器的需求。